Spool valve for rock drills



May 18 1926.

L. C, BAYLES SPOOL VALVE FOR ROCK DRILLS Filed Oct. 16, 1922 6 Sheets-Sheet 1 w ms May 18 1926. 1,584,715

L. C. BAYLES SPOOL VALVE FOR ROCK DRILLS Filed 001:. 16, 1922 6 Sheets-Sheet 2 awuemtoz May 18,1926. 1,584,715

L. c. BAYLES SPOOL VALVE FOR ROCK DRILLS Filed 16. 1922 6 Sheets-Sheet 3 gvwemtoz May as, am 158mm 1.. c. BAYLES SPOOL VALVE FOR ROCK DRILLS Filed Oct. 16 1922 a Sheets-Shea: 4

g Ed I m P :7 6 naw/14 696 May 18 1926. 1,584,715

L. C. BAYLES SPOOL VALVE FOR ROCK DRILLS Filed 16. 92 6 Sheets-Sheet '5 K 21 s 14 1s fi 3110044 602 j Zeuria 6132:7111;

May 18, 1926. 1,584,715

L. C. BAYLES SPOOL VALVE FOR ROCK DRILLS Fil 16. 1922 '6 Sheets-Sheet 6 INVENTOR CZB yleS.

' H15 ATTOR Y l atented May 1 8, i926.

T A l E S rarest series.

Lnwrs counter BAYLn-s, or nnsroiv, PENNSYLVANIA, assrenon r inane-som- RAND COMPANY, or anus-BY orrY, NEW JERSEY, A oortronarrou on NEW JERSEY.

SPOOL VALVE FOB ROCK 'DRILLS.

Application filed October 16, 1922.

This invention relates to fluid actuated rock drills, but more especially to a valve of the spool type for controlling the distribution of motive fluid to the cylinder of the ma -hine. The type of spool valve to which the invention relates is preferably provided with acentral head and outer heads at either side, and the valve controls both the admission of motive fluid to the cylinder and the exhaust from the cylinder.

lhe objects of the invention are to render the valve light, strong, quick acting and positive in its operation, so that it will start to move instantly under pressure fluid and te r inain held in one position in the cycle of operationsu'ntil ready to be thrown to the other position in the cycle, and will be able to continue reciprocating with certainty.

The valve may be constructed in various ways with three heads, but in accordance with my invention, the outer end of one outer head of the valve is formed with an actuating face and a separate holding face forming pressure'areas for actuating the valve in one direction and holding the valve until moved in the opposite direction, while independent means, preferably in the form of separate pressure areas, are provided on the valve for actuating the valve in the opposite direction and holding the valve until returned.

By constructing the valve with separate and distinct actuating and holding pressure areas, I am enoled to insure efiicient operatien at all tire and produce valves of different forms for special purposes all operaton substantially the some fundamental )rn'iciples.

The invention is illustrated in the accompanying drawings, showing so much a rock drill as will serve to make the invention clear, and in which Figure 1 is a diagrammatic longitudinal sectional elevation partly broken away through a portion of the cylinder and through the valve chest of a rock drill with the va ve in one position,

Figure 2 is a view similar to Figure 1 vith the valve in the opposite position. In both Figures 1 and 2 the inlet is at the center of the valve and the exhaust at the ends,

Figure 3 is a diagrammatic longitudinal sectional view of a modification having a valve like that shown in Figures 1 and 2 Serial No. 58 -,728.

but with the exhaust at the center of the valve and the inlet at the ends,

Figure 4 is a diagrammatic longitudinal sectional view of a modified form of valve construction with the inlet at the center and theexhaust at the ends of the valve,

Figure 5 is a view of aniodification of the valve shown in Figure l with the inlet at the ends and the exhaust at the center of the valve,

Figure 6 is a view of a modification of the valve in which theends of the valve are dissimilar, one end being like that shown in Figure 1 and-the other being like that shown in Figure 4:,

Figure 7 is a view of a modification in which the holding pressure areas at each end, of the valve are dissimilar,

Figure 8 is'a view of a modification having a differential valve,

Figure 9 is a. view of a modification of Figure 8 in which the differential valve is differently constructed,

Figure 10 is a view of another modiiication of a differential valve, and

Figures 11 and 12 are similar views of further inodiiications of differential valves.

Referring to the drawings, a portion of the cylinder A of a rock drill is indicated havinga reciprocating piston 13 adapted to impart blows of impact to a drill steel in the usual manner, if it be assumed that the machine isa hammer drill, although the invention n'iay beapplied to a piston drill in which the drill steel is bodily reciprocated by the piston or to other impact tools. The cylinder is provided with the usual back hea d C and front cylinderwasher D, and the distribution of motive fluid to the cylinder is controlled by a valve E in the valve chest F.

In Figures 1 and 2 the valve is formed with a central head G which controls the admission of pressure fluid to the cylinder, and outer heads H and J-at either side, conuected'to the central head G as-by means of thestems or necks K and L, which-arepreferably hollow in order to lighten the construction. In this instance, the outer heads HandJ are also hollow and by this means I form the outer end of each headuvith an actuating face 0 and a separate holding face P forming pressure areas. Plugs Q, and R form closures for the ends of'the valve chest F, and as shown are provided with redujcd portions adapted to enter the hollow heads H and J of the valve, as the valve recipro cates.

The pressure chamber S in which one actuating face 0 of the valve operates, cemmunicates with the cylinder Jr at a por T uncovered by the piston B near the end of its stroke in one direction, as indicated in Figure 1, and the other pressure chamber S in which the other of the said actuating faces 0 of the valve operates, communicates with the cylinder at a port U uncovered by the piston B near the end of its stroke in the opposite direction, as indicated in Figure 2. lhe plugs Q and are provided with passages V and XV registering with the pi X and Y in the cylinder, leading to the ports T and U respectively.

Each pressure chamber a in which one of the holding faces P operates, is at all times in communication with that end of the cy inder to which the piston has moved when it uncovers the port leading from the valve actuating pressure chamber S at the same end of the valve, and this accomplis through the passages Z) and c, in instance leading from the holding pressure chambers a to the inlet passages (Z and e which lead from the valve chest to the cylinder, for supplying and exhausting motive fluid to and from both ends of the cylinder. in Figure 1, it will be observed that the helding pressure chamber a at the right hand end of the valve, is in communication with the forward end of the cylinder through the passages 0 and e, which is the end of the cylinder to which the piston has moved when it uncoves the port T leading from the valve actuating pressure chamber S at the same end of the valve. Likewise it will be observed that the holding pressure chamber a at the left hand end of the valve, is in communication with the rearward end of the cylinder through the passages Z) and (Z, which is the end of the cylinder to which the piston has moved when it uncovers the port U leading from the valve actuating pressure chamber S at the same end of the valve.

In Figures 1 and 2 the valve chest is provided with an inlet at the center, controlled by the central valve head G and the outer valve heads H and J control the main exhaust ports 9 and h respectively at the ends of the valve. If desired, the outer valve hea' H and J may be provided with the rad bleeder ports 70 and 0 respectively dapred to register momentarily with one or the other or" the main exhaust ports, depending, of course, upon the position of the valve, for relieving the pressure in one of the valve actuating pressure chambers S at the proper time. The radial bleeder ports 7/ and 0 are preferably so positioned in the end heads TI and d that they ill register with their respective exhaust port, or in other words,

the forward end oi its stroke and returning on its rearward strolce. Under such ..-iuitions. motive iiuid entering the inlet 7' p:' s :Il'Ol id the valve stem L and through the inlet passage 0 to the forward end of the cylinder, to return the piston. Live pr to fluid pissing through the p go sure amber a at the right hand end of the valve, and the pressure upon the holding tac H i the valve holds the valve in positi n lo the actuating lace O oi? the valve n the actuating: pressure chamber S is open to atmosphere through bleeder port 0 and also open to exhaust through the passages v and X and the port i opening into the rearward end of the cylinder. The exhau-t from the rearward end of the cylinder pa :es thro (Z out through the valve wvardly, the

t 2 is uncover- 1 port 1 is cm'ered and the per chamber i reponderance of the presat that :e on the op ing e opposite end of the fact that said last named causes the valve to eatcd in Figur ward end of the cylineer to exhaust through the passage (2 and exhaust po t 71, and admitting live pressure fluid to the rearward end of the cylinder behind "he piston from the inletthrough the passage (Z. '.he holdir fa e P at. the forward or right hair; of the valve is then open to atmosphere through the passages c and (I. while the holding i'acc l. at the rearward end or left hand end (rt the valve is subject to live nre tiuid through the pa (Z and 7) thus holding the valve in its ton ward 120 ion until ready to be thrown rearivartlh; again. As shown in Figure 2 the pressure chamber at the rearward end of the valve orilll-.; llt'l'-'; through bloc-err port 7: 0 open to e:-:lnuu-:t

i and Y. The cvcie .hns repeated as the ti-ton shown in Figures 1 and 2, except that the central head G and the valve stems. K and L, are shown diagrammatically in section, and are solid instead of being hollowed. In Figure 3, however, supply of motive fluid is carried to the valve chest and cylinder through the inlet port-s and at the ends of the valve, while the central port 7 in the valve chest, is he exhaust port. In the modification shown in Figure 3, it is necessary to so arrange and locate the passages X and Y leading to the ctuating pressure chambers S and the passages h and 0 lead ing to the holding pressure chambers a, that the valve will function properly. For this purpose, the passages I. and Y leading to the ports 'l and U resp ctively, are not crossed as in Figures 1 and 2, and the passages Z) and c are. crossed and led to the passages and (Z respectively. The actuating pressure chambers S in Figure are provided with "leeder' ports 0 ailording communication between the passages V and lV and the atmosphere. 'l he operation of the piston and valve shown in Figure 3 is like that heretofore described, in connection with Figures land 2. As the piston returns on its rearward stroke, as indicated in Figure 3, and uncovers the port T, live pressure fluid is admitted through the passages X and V to the actuating face Q at the forward end of the valve. The actuating face O at the op posits end of the valve was open to atmosphere through the passages W and Y and thence through the rearward end or the cylinder through the passages (Z to the exhaust port 2", so that p1 .onde'a-nce of the pressure on the actuating face 0 at the forivard end of thevalve ov r the pressure on the holding "lace l? at the opposite end of the valve will throw the valve rcarwardly. Live PIGSSHO fluid will then be admitted L through the face l at the forward end of the valve. On the forward strokeof the piston, with the valve in its rearward position, live pressure fluid is admitted to the actuating pressure chamber S at the rear ard end of the valve,

soon as the port ll is uncovered by the piston, as indicated in the position oi 'the parts in Fi 'ure 3. lhe valve is then thrown 1'01"- ward to the position indicated, and live pressure fluid is admitted to the holding pressure chamber a, at the rearward end or the valve through the passages c and Z). The cycle o1 operations is repeated during the operation of t 1e machine.

in Figure el modification of the invention shown opt ating upon the principles heretofore icse'd, in which the valve Z is 1 rovithu with three heads, 1 and u, connected by tne stems L and li, but the outer heads tend u instead of being hollow, in order to form separate and distinct pressure surfaces, are in this instance provided with repassagis (Z and c to the holdingv duced extensions 0 and to operating within the hollow plugs a2 and y. The actuating faces or pressure areas 2 and 3, are in this case formed on the main portions of the heads t and it while the separate and distinct holding faces or pressure areas t and 5 are formed at the ends of the reduced extensions '2; and co. The actuat "faces 2 and 3 open to in the pressure chambers (3 while the holding faces 4- and 5 operate in the pressure chambers 7 in the plugs :12 and y. The actuating pressure chambers 6 are preferably formed with bleedcr ports 8 connected to the exhaust ports 9 and it. The ports and passages for the distribution of motive fluid to both ends of the cylinder and to both ends of the valve, are like those indicated in Figures 1 and 2, and the supply of motive fluid'is at the inlet 7 in the center of thvalve, while the exhaust takes place at the exhaust ports 9" and h at theiends of the valve.

l igure 5 shows modification similar to Figure at except that the exhaust takes placeat the center ol the valve through the em haust port 1 while the supply is admitted at the inlets p and g at the ends of the valve. lt also necessary to lead the passages X and Y to the cylinder without crossing them, as in Figure l, and the assages Z) and 0 are crossed and connected to the distribution passages c and (Z respectively, which is the reverse of the connections shot-1n in Figure 4L and similar to the connections shown in Figure 3.

In Figure 6, a modification of the invention is shown in which the valve Z is shown with a central head a and one outer head H of hollow form like the head shown in Figure 1, and another uter head a like the head shown in Figure 5, having a reduced extension "w. One plug. Q is adapted to enter the hollow head H, while the other plug g is provided with a recess, in which the extension ec enters. Motive fluid is supplied at the central inlet in the valve chest and exhausted at the exhaust ports 9 and h at the ends of the valve, so that the arrangement of ports and passages for the valve and cylinder are like those indicated in Figures 1, 2 and 4 except for the fact that the passage 0 at the forward end of the valve leading to the holding "pressure chamber 7 here communicates directly with the forward end of the cylinder instead of with the dis triloution passage 6 without, however, changing the fimction of the passage 0. It is not necessary in all cases to provide the bleeder ports for the actuating pressure chambers of the valves and they have been omitted in Figure 6, because the said actuating pres sure chambers are respectively open to atmosphere through the respective exhaust ports, in any event, substantially at the instant that the valve is thrown, and there is also a certain amount otl akage at all one oi the valve actuating chambers, and is a prelcr; )Je ceustrin-tum. The operation of the valve and piston in i igure (3 is lilte that dcscrihcd in connection with Figures 1, 2 and l.

in the niodilicatiini shown in l igure the valve ii is termed with the central head a like Figure (3 and the hollow outer head ll: also like l igure (3. The other outer head l (l is hollow, hut l'ornicd with thichcr walls than the head ll, thus providing an actuating lace 0 ol smaller area than the opposite actuating lace (1, and also forming a hoidug lace l of la 'ger area than the opposite iolding lace l. in order to reduce the presure in the holding pressure chan'iher a at 1e "forward end ot the valve, a hleeder port 2 is provided through the plug R from said chamber to the atmosphere. In Figure 7 the iassage c purposely made small and the ileeder port 12 is provided in order that the pressure in the holding chamber a shall. at all times be considerably lower than the motive fluid pressure entering the drill. Since in Figure 7 the inlet is 1 t the center of the valve and the exhaust ports are at the ends of the valve, the distribution ports and Q s. ges for the valve and cylinder are substantially like those indicated in Figures 1 and 2 with the exception ot the passage 0 which is led directly to the forward end of the cylinder, as in Figure 6, and the operation and function of the parts is like that indicated for Figures 1 and In Figure 8, a modification ot the inven tion is shown in which a differential valve 13 is provided in the valve chest 14, which valve has a cent al head 8 and one outer hollow head 15 of larger outer diameter than the central head 8, while the other outer head 16 is or the same diameter as the central head 3 and as shown is a solid head having no reduced extension, although the head 16 may he made hollow for lightness. lhe valve plug Q at the rearward end of the valve is alapted to enter the hollow head 15 and this head is provided with the :ictuating pr ssure time 0 and the holding pressure face 1 as in Figure 1. The shoulder 1'? formed on the head 15 being of larger area than the tace of the central head a con stitutes a holding pressure tace opposed to the holding pressure tace P and the outer end 18 oi? the opposite outer head 16 forms the actuating pressure face, opposed to the actuating pressure face 0. Pressure fluid is supplied to the machine through the inlets p and Q" at the outer ends of the valve, and the exhaust takes place at the central exhaust port r. The distribution passa es (Z and a lead from the valve chest to the outer ends of the cylinder and a passage X leads from the actuating pressure chamber if) for the actuating face 18, to the port 'l' in the cylinder. Similarly, passages V. and Y lead from the actuating pressure cl aznher H at the opposite end ol the valve to the port U in the cylinder. A. passage (3 connects the holding pressure chaiuhcr u at the rearward end of the valve with the di tii uiliou passage (2. The holding pressure surlacc l? is at all times in communication with one cud oi the cylinder through passage in the operation of the valve and pidon strewn in Figure. 8, let it he zusuiucd that e piston is starting to travel rcarwardl x. n which case the valve is in its forward posh as indicated. and motive lluid is lltli Huher u. at the rearward end of the valve, holding the valve forward- As soon as the piston uncovers the port- I in the cylinder, the live pressure fluid is admitted through the passage X to the actuating pressure chamher 19 at the forward end of the valve, and the pressure on the actuating face 18 preponderates over the pressure in the holding pressure chainher a. at the opposite end of the valve, causing the valve to he thrown rear vardly. Live pre" sare fluid is then admitted through the inl p and passage (Z to the rearvvard end of the cylinder, and the live pressure lluid on the holding pressure face 1. of the head 15 holds the valve rearwardly until it is ready to be thrown forwardly again as the piston uncovers the port U on its forward stroke. It is obvious from the modification disclosed in Figure 8 that separate and distincta "tuating and holding pressure faces may he provided on dill erent parts of the valve according to the construction or the "valve heads and depending on whether or not the valve is constructed on the differential principle. As indicated in Figure 8 there may he separate actuating and holdingl'zu s as one end of the valve, while the opposed actuating and holding faces need not necessarily he at the opposite end of the valve.

Another modification showing a dill'ereutial valve is illustrat id in Figure fl, in which the valve is provided with the central head 8, and one outer head 22 is a solid hea of larger diameter than the central head .i and provided with a reduced extension 2;. The opposite outer head 16 is like that indicated in Figure 8. The plug .11: at the rearward end of the valve is provided with a recess into which the reduced ext nsion i: extends and the head is formed with the actuating pressure face 2, while the end of; the reduced extension 0 forms a holding pressure face 4-. The actuating pro 'ure face 2 operates in the actuating pressure chamber mew-15 6 and the holding face all operates in the holding pressure chamber 7. The head 16 is provided with the actuatingface 18-.operating in the actuatingpressure chamber19. The surface c3 of the head 22 being of larger area'than the face of'the central head 3 forms a holding faceopposed to the holdin; faced; The ports and passages for the valve andcylinder in Figure 9 are like those illustrated in Figure 8, and the parts operate as described in connection with Figure 8.

In the modification shown in Figure 10, a

differential valve 24' is illustrated operating in the valve chest 25 and inithisinstance, the inlet is at the center of the valve, while the exhaust takes place at the exhaust ports 9 and it at the outer ends of the valve. The central head 26 is of the same diameter as the outer hollow head 15. while the opposite outer head 16 is of smaller diameter than eitherof the other two heads. In this modification, the surface 2? of the central head 26 being larger than the head 16, forms theholding face for holding the valve rearwardly, and otherwise the actuating and holding surfaces are like those shown in connection with the modification illustrated in Figure 8. Since the inlet is at the center of the-valve, the passages X and Y leading to the respective actuating pressure chambers 19 and S of the valve are crossed and the passage Z2 leading from the holding pressure chambera at the rearward end of the valve is connected to the distribution passage d.

In the operation of the modification shown in Figure 10 the piston is indicated'starting on its rearward stroke, and motive fluid is being admitted from the inlet f through the passage 0 to the forward end of thecylinder. Thevalve is being held rearwardly by live pressure fluid on the holding face 27 of the central head 26. lVhen the piston uncovers the port U in the cylinder, live pressure fluid passes through the passages Y and WV to the actuating pressure chamber S at the rearward end of the valve, and the valve is thrown forward by the preponderance of the pressure uponthe actuating face 0 since this face is of larger area than the holding face 27 of the central head 26. The valve is held in its forward position as long as necessary,

by live pressure fluid through the passage Z) leading to the holding pressure chamber a. As the piston travels forwardly and uncovers the port T, live pressure fluid is admitted through the passage X to the actuating pressure chamber 19 at the forward end of the valve, and the valve is caused to move rearwardly by the pressure on the actuating face 18. The cycle continues as the piston reciprocates.

In the modification shown in Figure 11, the valve 28 is like that shown in Figure 10 with the exception that the outer head 22 of the valve shown in Figure 9 is sub stituted for the head 15, andrlhe plug .11 cooperating'with the head'22 is used in place offthe. plug The ports and passages are arranged'and located in the same manner in Figure- 11; as in Figure 10, and the operation of the'va-lve in Figure 11 is like that in Figure 10, since the motive fluid. is supplied at the center inlet f and exhausted at the exhaust. ports 9 and it at the ends of the valve. @no possible advantage of the head 22 over the head 15 resides in the fact that the use of a peripheral flange on the head is avoided in order to obtain a holding face, and the valve head is thus made stronger because if the flange upon which the holding face P shown in Figure 10 is located, is made too thin, a weakness may result. The valve shown in. Figure 11 is preferaliily made as light possible, eliminating metal where possible, as for instance in the heads and in the stem, and these parts are preferably hollowed as indicated in the drawings.

In the modification shown in Figure 12, the valve is also like that shown in Figure 10 with the exception that the peripheral substantial thickness, thus producing a holding face P" of increased area, substantially like the holding faceP shown on the head 10 in Figure 7, and in order to reduce the pressure in the holding pressure chamber a2, a bleed'e-r port 12'is preferably provided leading to the atmosphere, as in Figure '7. The ports and passages in Figure 12 are like those shownin Figures 10 and 11, encept that the passage 3) is located directly in the head 30 in order to connect the holding pressure chamber a with a portion of the valve chest to which live fluid pressure is intermittently supplied;

It is obvious t-l'iat the different features shown in different modifications illustrated in the drawings, may be combined to form further modifications without departing from the spirit of the invention, as defined in the appended claims.

I claim:

1. In arock drill, the combination of a cylinder and reciprocating piston, a valve chest having a plurality of pressure chambers at each end, said valve chest having inlet passages leading to the cylinder and main exhaust ports leading to the atmosphere, a fluid actuated valve in said valve chest for controlling said piston, said valve having a central head to control the ad mission of pressure fluid to the cylinder and outer heads at either side to control the main exhaust ports, the outer end of one outer head of the valve havin an actuating face and a separate-holding face forming pressure areas, the pressure chamber in which the said actuating face operates communicating with the cylinder through a passage uncovered by the piston near the end of its flange of the hollow head 30 is made of lill;

stroke in one direction, and the pressure chamber in which the said holding face operates being; at all times in communication with that ad of the cylinder to which n has moved when it uncovers the 'ssnre chan'iher. independent means (jv'lllltlc and recip" 9 i locating piston, a valve chest having; a plurality oi pressure chami'ers at each end, said valve chest having inlet passages leadingto the cylinder and main eizlia istphere, a llu d aetuat d valve in said valve chest for controlling id piston, said valve having; a centra head to control the admission of pressure tluid to the cylinder, and outer heads of the diameter at either side to control rl exhaust ports, the outer ends of the outer heads of the valve each having an actuati lace and a separate holdinglace ton pressure areas, one of the pressure cham ers in which one of the said actuating; faces operates communicating with the cylinder through a passage uncovered by the piston near the end of its stroke in one direction, and the other pressure chamber in which the other of the said actuating faces operates communicating with the cylinder through a passage uncovered by the piston near the end of its stroke in the opposite direction, each pressure chamber in which one of the said holding laces operates being at all times in communi -ation with that end of the cylinder to which the piston, has moved when it uncovers the passage leading from the uilve actuating pressure chamber at the same end of the valve, said end heads having radia bleeder ports to register n'iomentarily with the main exhaust ports for erdiausting a porlion. of the pressure l'luid utilized or throwing the valve.

3. In a rock drill the combination of a cylinder and reciprocating piston, a *alve chest having a plurality of pressure chambers at each end. said valve chest havingin let passages leading to the cylinder and main exhaust ports leadine to the. at mospherc, and a fluid actuated v; lve in said valve chest for controlling said piston, said valve having a c nti'al head to control the admission of pres sure lluid to the cylindr, and outer heads ports leading to the atmossome from the said valve actuat-' ot the same diameter at either side to con trol the main exhaust ports, the outer ends of the outer heads of the valve each having an actuating face and a se arate holding lace forming pressure areas, one of said areas at ach end being formed on the outer head itself at that end, the pressure chambers tor the said actuating tacos connnunieating with the cylinder through passages on opposite sides of the center and adjacent to the center, the pressure chambers for the said holding taces COlnlllllllltillllll f' with the cylinder at all times through passages near the ends itarthcst away troni the poin which the pz'issa i'e-i for the said zii-luruiuuf r valve ends communicate jl.e cylinder, said end heads having: lilc-f-ilei' ports to re: rter lzNUlWilltH'llj-f 10 main exhaust pelts for eJ-Ihaustino' on elf the pressure lluid acting against. "uati faces of the valve.

4t. In a rock drill the combination of a lindcr and reciprocating piston, a valve iaving a plu 'ality of pressure cham each end. said valve chest having insagcs leading; to the ends oi" the cylinder and main exhaust ports leading; to the a mosphere, a l'luid actuated valve in said. valve chest for controlling said piston, said valve having a central head to control the admission of pressure fluid to the cylinder, and an outer head on either side to control the main exhaust ports, the outer ends of the outer heads of the valve each having an actinating face and a sepa ate holding face torming pressure areas, the press re chambers tor the said holding laces communicating; at all times vith the cylinder near the ends, the pressure chamber r the said actuating laces communicating with the cylinder at points between mid-ccnte' and the ends opposite to the ends with which the pres ure chambers for the said holding il'accs (Ollimunicatc, the Force exertml on each of said actuating faces being' greater than that e):- erted on, each of the said holding laces, said end heads having radial bleeder ports to register momentarily with the main exhaust ports for exhausting a portion of the pres-- sureutilized for throwing" the valve, said blecdcr ports being adapted to register with the main ejtliauil port located that end of the valve chest corrcs 'ionding with the end of the cylinder into which pressure fluid being admitted and during); such admission of pressure .tluid to the cvliruler.

In testimony whereof I have signed this specification.

LlGWlti C(flhlllUll l'li tl'llllt the sa lit) 

